Figure visualising the percent of a VO2max of 5.0 L/min required to produce functional threshold power (FTP) between 300 and 400 W, with isolines for gross metabolic efficiency (GE, %) from 20-25% and RER at each GE value between 0.85-0.95. The question was “is it possible to achieve an FTP of 380 W at a VO2max of 5.0 L/min (71 ml/kg/min at 71kg bodyweight)?” Based on these calculations, that would require somewhere around 24% GE and ~90% VO2max, which is just about physiologically plausible for an elite male cyclist… but would certainly take some work to achieve.
Post 2
Reasonable estimates for gross metabolic efficiency (GE) for trained cyclists is 15-25%
GE logarithmically increases with power output, so higher fitness = higher power = higher GE
Prediction model: GE = 0.0482 * log(power) - 0.0566
90% prediction interval for individual values is around ± 2.5%
Figure plotting individually observed gross efficiency (GE) values for cyclists across power output from 50 to 450 W, taken from published cross-sectional data in Ettema & Lorås, 2009. Efficiency in Cycling. A Review. https://www.researchgate.net/publication/24027428_Efficiency_in_cycling_A_review. A logarithmic model predicts GE as a function of PO, with 90% prediction intervals equivalent to ± 2.5% around the marginal estimate. e.g. at 250 W estimated GE = 21%, 90% PI = [18.5, 23.5].
Post 3
GE prediction model derived from data in Ettema & Lorås, 2009 (link in 📊Alt text)
Most of the variance in GE comes from differences in cadence. Most of the rest comes from random cross-sectional individual differences
GE is probably trainable, but veeery slowly
Figure reproduced from Ettema & Lorås, 2009. Efficiency in cycling: a review. Figure description reads: Fig. 2 Overview of literature data explored in this review and used in the quantification of efficiency. The different symbols indicate different studies. Figures a–d show the mean values at a particular cadence or external power for each study. a Gross efficiency against cadence. b Same data against external power… d Same data as in b, but depicting a possible error of measurement of 5%. Thick curve is the average curve, based on the regression line in b. Thin curves indicate ranges if both metabolic rate and external power have deviation (error) of 5%, but in opposite directions. A thick vertical error bar indicates the same range if only one of the measures has a 5% deviation; the thin horizontal arrows indicate the efficiency difference following from this error.
Post 4
Typical reported range for fractional threshold (%VO2max @ CP, FTP, MLSS, VT2, LT2, etc) in trained cyclists is anywhere from 75-90%+, possibly higher in elite and female athletes
I can’t find a good dataset for cyclists right now, so here is one for treadmill running (link & details in 📊Alt text)
Figure & table from Benítez-Muñoz et al, 2024. Differences in the ventilatory thresholds in treadmill according to training status in 971 males and 301 females: a cross-sectional study. https://pmc.ncbi.nlm.nih.gov/articles/PMC11829848/. Showing percent VO2max at ventilatory threshold 2 (close equivalence to critical power or functional threshold power) across a range of fitness levels in runners, from 85-92%. Running threshold will tend to be slightly higher %VO2max compared to cycling threshold, hence the low-end fitness estimate is higher than typically observed in cyclists. But the high-end estimate is probably similarly bounded around 90-92%.
Post 5
RER is a function of exercise intensity and substrate (lipid/glucose) oxidation
At threshold, RER will be ~0.85-0.95, maybe up to 1.00 by the end.
Along each GE isoline in the top figure, RER equates to a small difference of 2 %VO2max. GE drives the big differences
Post 6
So for this specific question “is it possible to achieve an FTP of 380 W at 5.0 L/min VO2max?”
The answer is yes, with elite-level metabolic efficiency ~24% and fractional threshold ~90%VO2max
*How* to achieve that is an entirely different question which I don’t have code for (yet 😉)
Figure plotting individually observed gross efficiency (GE) values for cyclists across power output from 50 to 450 W, taken from published cross-sectional data in Ettema & Lorås, 2009. Efficiency in Cycling. A Review. https://www.researchgate.net/publication/24027428_Efficiency_in_cycling_A_review. A logarithmic model predicts GE as a function of PO, with 90% prediction intervals equivalent to ± 2.5% around the marginal estimate. e.g. at 250 W estimated GE = 21%, 90% PI = [18.5, 23.5].
Figure reproduced from Ettema & Lorås, 2009. Efficiency in cycling: a review. Figure description reads: Fig. 2 Overview of literature data explored in this review and used in the quantification of efficiency. The different symbols indicate different studies. Figures a–d show the mean values at a particular cadence or external power for each study. a Gross efficiency against cadence. b Same data against external power… d Same data as in b, but depicting a possible error of measurement of 5%. Thick curve is the average curve, based on the regression line in b. Thin curves indicate ranges if both metabolic rate and external power have deviation (error) of 5%, but in opposite directions. A thick vertical error bar indicates the same range if only one of the measures has a 5% deviation; the thin horizontal arrows indicate the efficiency difference following from this error.
Figure & table from Benítez-Muñoz et al, 2024. Differences in the ventilatory thresholds in treadmill according to training status in 971 males and 301 females: a cross-sectional study. https://pmc.ncbi.nlm.nih.gov/articles/PMC11829848/. Showing percent VO2max at ventilatory threshold 2 (close equivalence to critical power or functional threshold power) across a range of fitness levels in runners, from 85-92%. Running threshold will tend to be slightly higher %VO2max compared to cycling threshold, hence the low-end fitness estimate is higher than typically observed in cyclists. But the high-end estimate is probably similarly bounded around 90-92%.